Method of exchanging data packages between first and second portable communication devices using a favoured frequency band

ABSTRACT

The present disclosure relates in a first aspect to a method of exchanging data packages between a first portable communication device and a second portable communication device over a bi-directional wireless communication channel, where at least one of the first and second portable communication devices comprises a hearing instrument. The method comprises generating, by the first portable communication device, a plurality of data packages over time and transmitting the plurality of data packages from the first to the second portable communication device through a plurality of spaced apart frequency bands distributed across a predetermined radio frequency range of the bi-directional wireless communication channel. The method further comprises computing, at the first wireless communication device or at the second wireless communication device, respective transmission quality estimators of the plurality of spaced apart frequency bands and determining a favored frequency band based on the detected transmission quality estimators.

RELATED APPLICATION DATA

This application claims priority to and the benefit of Danish PatentApplication No. PA 2015 70536 filed on Aug. 18, 2015, pending, andEuropean Patent Application No. 15181382.1 filed on Aug. 18, 2015,pending. The entire disclosures of both of the above applications areexpressly incorporated by reference herein.

FIELD

The present disclosure relates in a first aspect to a method ofexchanging data packages between a first portable communication deviceand a second portable communication device over a bi-directionalwireless communication channel, where at least one of the first andsecond portable communication devices comprises a hearing instrument.The method comprises generating, by the first portable communicationdevice, a plurality of data packages over time and transmitting theplurality of data packages from the first to the second portablecommunication device through a plurality of spaced apart frequency bandsdistributed across a predetermined radio frequency range of thebi-directional wireless communication channel. The method furthercomprises computing, at the first wireless communication device or atthe second wireless communication device, respective transmissionquality estimators of the plurality of spaced apart frequency bands anddetermining a favoured frequency band based on the detected transmissionquality estimators.

BACKGROUND

Wireless bi-directional or unidirectional streaming of audio databetween a pair of hearing instruments, or a hearing instrument andanother portable communication device, is highly desirable. Thereexists, however, a number of technical problems in terms of powerconsumption, reliability, transmission latency or delay, component sizeetc. with prior art wireless data communication methodologies, protocolsand devices that must be addressed to deliver a feasible solution for ahearing instrument due to the small amount of power available fromtypical batteries of hearing instruments.

Standardized wireless data communication protocols such as Bluetooth LEas defined by the Bluetooth Core Specification 4.1, or earlier versions,does not allow for real-time audio transport. There are a number oflimitations in the protocol as defined that means that real-time audiotransport is unfeasible without changing certain protocol layers:

-   -   The nature of the L2CAP channels as defined for LE—where a best        effort approach for data transport with no timeouts or flushes        on transmissions is defined—also means that it is next to        impossible to do a real-time audio service over LE as defined.    -   The lack of real-time transport means also means that stereo        synchronization between two paired audio sinks (such as hearing        aids) is next to impossible.    -   The packet size means that the overhead data for transmitting        the required data rate for real-time audio (typically 16-96        kbit/s) is very high.

It is an object of the present method of exchanging data packagesbetween the first and second portable communication devices to overcomethe above-mentioned problems and shortcomings of the prior art wirelessdata communication methodologies, protocols and devices.

SUMMARY

A first aspect of one or more embodiments described herein relates to amethod of exchanging data packages between a first portablecommunication device and a second portable communication device over abi-directional wireless communication channel, where at least one of thefirst and second portable communication devices comprises a hearinginstrument. The method comprising:

-   -   generating, by the first portable communication device, a        plurality of data packages over time,    -   transmitting the plurality of data packages from the first to        the second portable communication device through a plurality of        spaced apart frequency bands distributed across a predetermined        radio frequency range of the bi-directional wireless        communication channel,    -   receiving, at the first portable communication device, a        plurality of data packages over time from the second portable        communication device,    -   computing, at the first wireless communication device or at the        second wireless communication device, respective transmission        quality estimators, such as respective packet error ratios        (PERs), of the plurality of spaced apart frequency bands,    -   determining a favoured frequency band based on the detected        transmission quality estimators,    -   transmitting, from the first to the second portable        communication device, a first data package of the plurality of        data packages a first time on the favoured frequency band.

In some embodiments of the present methodology, each of the first andsecond portable communication devices comprises a hearing instrument orhearing aid—for example jointly forming a wireless binaural hearing aidsystem. In the latter embodiment, each of the first and second hearingaids may receive and deliver a binaurally processed hearing losscompensated audio signal to a user or patient via respectiveloudspeakers or receivers as discussed in further detail below withreference to the appended drawings. Each of the first and second hearinginstruments or aids may comprise a BTE, RIE, ITE, ITC, CIC, etc. type ofhearing instrument. Typically, only a severely limited amount of poweris available from a power supply of a hearing instrument. For example,power is typically supplied from a conventional ZnO₂ battery in ahearing aid. In the design of a hearing aid, the size and the powerconsumption are important considerations. In other embodiments of thepresent methodology, one of the first and second portable communicationdevices comprises another type of battery powered audio-enabled devicethan a hearing instrument such as an earphone, headset, smartphone,remote microphone array, remote signal processor etc.

The plurality of spaced apart frequency bands may comprise between 60and 120 frequency bands such as between 70 and 100 frequency bands,spanning across the predetermined radio frequency range. A bandwidth ofeach of the frequency bands may lie between 0.5 MHz and 3.0 MHz. Theplurality of spaced apart frequency bands may be located in theindustrial scientific medical (ISM) radio frequency range or frequencyband such as the 2.40-2.50 GHz band or the 902-928 MHz band. Theplurality of spaced apart frequency bands may alternatively be locatedin another suitable frequency band. In some embodiments, thebi-directional wireless communication channel may be based on near-fieldmagnetic coupling between inductive coils of the first and secondportable communication devices. In the latter embodiment, the pluralityof spaced apart frequency bands may be arranged in a radio frequencyrange below 2 GHz, for example below 1 GHz, or below 500 MHz.

The determination of the favoured frequency band, also designated thegolden frequency band, means that the first data package is likely to betransmitted a first time on a frequency band with particularlyfavourable data transmission qualities, e.g. a low packet error ratio(PER). Hence, maximizing the likelihood of a successful first timetransmission of the first data package from the first to the secondportable communication device. This feature is advantageous even where acommunication protocol, controlling the exchange of the plurality ofdata packages over the bi-directional wireless communication channel,allows for a limited number of retransmissions of the first data packageas discussed in further detail below. There are numerous benefits ofusing the favoured or “golden” frequency band in the first attempt totransmit the first data package, or to transmit a second data package asdiscussed below, particularly if the first data package comprises audiodata, e.g. one or more audio frames. The frequency band with the lowestPER is preferably selected as the favoured frequency band and its lowPER maximizes the likelihood of a successful first attempt transmissionof one or both of the first and second data packages thereby reducingaudio frame latency. The use of the favoured frequency band mayadditionally be very helpful to reducing power consumption for asuccessful transmission of the first data package and/or the second datapackage, because the number of retransmissions of the data packages isminimized in a statistical sense.

The respective transmission quality estimators may be computed by afirst communication controller of the first wireless communicationdevice and/or by a second communication controller of the secondwireless communication device as discussed in further detail below. Insome embodiments, the respective transmission quality estimators may becomputed by only one of the first and second communication controllersand thereafter transmitted to the other communication controller via aheader field or portion of the plurality of data packages as discussedin further detail below with reference to the appended drawings.

As mentioned, the present method of exchanging data packages maycomprise a further step of transmitting, from the second to the firstportable communication device, the second data package of the pluralityof data packages a first time on the favoured frequency band.

Each data package of the plurality of data packages generated andtransmitted by the first portable communication device may comprise aheader section, a payload section and a data check section holding apackage error-detection code. The error-detection code may comprise aCRC code, as discussed below in further detail, and allow the first andsecond portable communication devices to check the validity of the dataof a received data package before utilizing the data of the data packagein question.

Each data package of the plurality of data packages generated andtransmitted by the second portable communication device may likewisecomprise a header section, a payload section and a data check sectionholding a package error-detection code.

One embodiment of the present methodology may comprise a step of:

-   -   adding a band identifier indicating the favoured frequency band        to a predetermined header field of the header section of each of        the first and second data packages. This embodiment allows the        first and second portable communication devices to track changes        in the identity of the favoured or golden frequency band over        time as RF noise conditions changes over time as discussed in        further detail below with reference to the appended drawings.

According to one embodiment of the present method of exchanging datapackages a first subset of the plurality of data packages transmitted bythe first portable communication device belongs to a first packetcategory comprising audio data and a second subset of the plurality ofdata packages belongs to a second packet category without audio data. Asize of data packages belonging to the second packet category may besmaller than a size of data packages belonging to the first packet

The audio data may comprise a plurality of samples or values of adigital audio signal, such as a sequence of discrete-time anddiscrete-amplitude digital audio signal values that representcontinuous-time and continuous-amplitude values of an analogue audiosignal that can be converted into acoustic sound. In other words, theaudio data and frames contain encoded digital data that are intended forconversion into sound at some point in time as is well-known in the artof streaming audio.

Another embodiment of the present method of exchanging data packagescomprises steps of:

-   -   establishing a plurality of successive connection events over        time through the bi-directional wireless communication channel;        and        during at least a subset of the plurality of successive        connection events:    -   transmitting at least the first and second data packages the        first time on the favoured frequency band.

The skilled person will understand that a first data package, a seconddata package, and optionally a third data package as discussed below,may be transmitted during each connection event of the plurality ofsuccessive connection events or at least during the subset of successiveconnection events. According to the latter embodiment, this firstattempt to transmit the first data package and/or first attempt totransmit the second package may be the first attempt to transmit thefirst data package of each connection event and/or the first attempt totransmit the second data package of each connection event.

The first and second portable communication devices are physicallyconnected during each of the plurality of successive connection eventsand may be physically disconnected during intervening idle time periods.Hence, the plurality of consecutive connection events may be separatedby intervening disconnect or idle time periods without data packageexchange between the first and second portable communication devices.Hence, each pair of successive connection events may be separated by adisconnect period or idle time period. The time separation, ortransmission interval, between a pair of adjacent connection events maylie between 2 ms and 20 ms such as between 5 ms and 10 ms. The timeseparation, or transmission interval, may be fixed as long as the firstand second portable communication devices are logically connecteddespite the physical disconnection during the idle time periods. Thedurations of the successive connection events will generally varydepending on the required number of retransmissions of the first and/orsecond data packages in any particular connection event, the channeldata rate and a size or length of the data packages. The duration ofeach of the successive connection events may for example lie between 0.5ms and 5 ms such as between 0.9 ms and 2.5 ms as discussed in furtherdetail below with reference to the appended drawings. The method ofexchanging data packages may comprise further steps of:

-   -   powering down respective transceiver circuits of the first and        second portable communication devices during the disconnect time        periods. This powering down or idling of the respective        transceiver circuits may lead to considerable power consumption        savings in each of the first and second portable communication        devices as discussed in further detail below with reference to        the appended drawings.

The above-discussed embodiment of method of exchanging the data packagesthrough the plurality of successive connection events may comprise stepsof:

-   -   if the first transmission attempt of the first data package        fails, retransmitting the first data package for at the most N        times during each connection event if the first data package        belongs to the first packet category; and/or    -   if the first transmission attempt of the second data package        fails, retransmitting the second data package for at the most M        times during each connection event if the second data package        belongs to the first packet category;        N being a positive integer between 1 and 4 and M being a        positive integer between 1 and 4.

If the first transmission attempt of the first data package failsdespite the use of the favoured frequency band, this may indicate lessfavourable transmission qualities through or on the golden frequencyband than expected. One embodiment of the present methodology maytherefore comprise steps of:

-   -   selecting, in accordance with a predetermined frequency hopping        key, a different frequency band of the plurality of spaced apart        frequency bands than the favoured frequency band,    -   retransmitting the first data package on the different frequency        band; and optionally:    -   transmitting, during the connection event, subsequent data        packages to the retransmitted first data package on different        frequency bands selected in accordance with the predetermined        frequency hopping key. The different frequency band for the        first retransmission of first data package and the different        frequency bands for the transmission of the subsequent data        packages, after the second data package has been transmitted on        the golden frequency band, are selected in accordance with the        predetermined frequency hopping key or algorithm in this        embodiment.

A relatively simple frequency hopping scheme or key may be utilizedwhere a random hopping key is generated by a master device of the firstand second portable communication devices. The master device may computethe selected frequency band by executing or computing the random hoppingkey or algorithm and transmit the random hopping key to the otherportable communication device which may be configured as slave device.Each of the first and second portable communication devices maythereafter use this random hopping key to select the appropriatefrequency band to transmit and receive a particular data package on. Thenext frequency band of the plurality of spaced apart frequency bands maybe selected as the previously used frequency band plus the hopping key.If the computed frequency band exceeds the number of available frequencybands, a modulus operation is preferably applied to the hopping key todetermine or compute a frequency band within the available number offrequency band.

According to one embodiment of the present methodology, the frequencyhopping key or scheme is computed according to the following equation:f _(n+1)=(f _(n) +h) % p; wheref_(n) represents the frequency band at time instant n;h represents the hopping key and n, h>=0 and positive integers;% represents the modulus operator;p is the number of spaced apart frequency bands.

The modulus value, %, may be selected to a prime number closest to thenumber of utilized frequency bands for example between 60 and 120. Ifthe number of frequency bands is set to 78 the modulus value mayaccordingly be set to the closest prime number to 78 which is 79. Theuse of a prime number is preferable because it provides a gooddistribution of the transmitted data packages across the number ofavailable frequency bands.

One embodiment of the present methodology is based on data packageswhich comprise positive acknowledgement indicators to expresslyacknowledge a successful receipt at the receiving portable communicationdevice of a particular data package to the transmitting portablecommunication device. One embodiment of the present methodology maytherefore comprise steps of:

-   -   adding acknowledgement indicators, at the first portable        communication device, to the plurality of data packages        transmitted from the first to the second portable communication        device wherein at least a subset of the acknowledgement        indicators indicates whether a previous data package to a data        package to be transmitted was successfully received at the first        portable communication device; and    -   adding acknowledgement indicators, at the second portable        communication device, to the plurality of data packages        transmitted from the second to the first portable communication        device wherein the acknowledgement indicator of each data        package to be transmitted indicates whether a previous data        package was successfully received at the second portable        communication device.

One such embodiment of the present methodology comprises, during eachconnection event of the subset of successive connection events, furthersteps of:

-   -   monitoring the wireless communication channel, at the first        portable communication device, for the second data package; and    -   receiving the second data package at the first portable        communication device, if the acknowledgement indicator of the        second data package is set:    -   generating, at the first portable communication device, a third        data package comprising an acknowledgment indicator setting        reflecting successful or failed receipt of the second data        package,    -   transmitting the third data package to the second portable        communication device through the wireless communication channel;        or        if the second data package is absent or the acknowledgement        indicator of the second data package is unset:    -   setting the acknowledgment indicator of the first data package        to reflect a failed receipt of the second data package and        retransmitting the first data package from the first to the        second portable communication device,        wherein the retransmission is carried out for a maximum of N        times if the first data package belongs to the first packet        category. N is the previously discussed positive integer.

On the other hand, if the first data package belongs to the secondpacket category, the method may proceed by discarding or droppingretransmission of the first data package in response to the absentsecond data package or in response to the unset acknowledgementindicator of the second data package. In the latter embodiment, themethod may comprise a further step of flushing or abandoning the firstdata package when the first data package belongs to the second packetcategory for the reasons discussed below. The first communicationcontroller may in some embodiments likewise be configured to discardingretransmission of the first data package and flushing the first datapackage if the data of the second package are flagged as invalid by theerror-detection code of the second data package as discussed below infurther detail.

Generally, if the error detection code indicates that data of aparticular received data package are invalid, the data, in particularthe acknowledgment indicator, may be ignored and the acknowledgmentindicator of a subsequently transmitted data package set to reflectfailed receipt of the data package in question. Hence, the method ofexchanging data packages may comprise further steps of:

-   -   checking an error-detection code of the second data package        subsequent to receipt of the second data package at the first        portable communication device,    -   if the error-detection code indicates invalid data of the second        data package:        ignoring the setting of the acknowledgment indicator of the        second data package and unset the acknowledgment indicator of        the third data package to reflect failed receipt of the second        data package. The third data package may belong to the second        packet category.

The skilled person will understand that a second portable communicationdevice configured to carry out the present methodologies of exchangingdata packages may operate in a corresponding manner to the firstportable communication device with respect to receipt, generation,transmission and retransmission of data packages of the first and secondpacket categories such as the second data package. Hence, one embodimentof the present methodology may comprise, during each connection event ofthe subset successive connection events, further steps of:

-   -   monitoring, at the second portable communication device, the        bi-directional wireless communication channel for the first data        package transmitted by the first portable communication device,    -   receiving the first data package at the second portable        communication device, and    -   generating, by the second portable communication device, the        second data package with the acknowledgment indicator setting        reflecting successful or failed receipt of the first data        package,    -   transmitting the second data package from the second to the        first portable communication device through the bi-directional        wireless communication channel,    -   monitoring, at the second portable communication device, the        bi-directional wireless communication channel for the third data        package or for the retransmitted first data package from the        first portable communication device subsequently to receipt of        the second data package,    -   receiving the first data package or the third data package at        the second portable communication device, and        if the acknowledgement indicator of the first or third data        package is set:    -   discard further transmission of the second data package; or        if the acknowledgement indicator of the first or the third data        package is unset or if the first and third data packages are        both absent:    -   retransmitting the second data package from the second to the        first portable communication device for at the most M times if        the second data package belongs to the first packet category. M        is the previously discussed positive integer.

The latter embodiments of the present methodology of exchanging datapackages, i.e. comprising at the most N retransmissions of the firstdata package of the first packet category and/or comprising at the mostM retransmissions of the second data package of the first packetcategory, are based on a limited number of retransmission of lost datapackages of the first packet category. A data package of the firstpacket category comprises audio data or frames which for example may beheld or stored in a payload section of the data package as discussed infurther detail below with reference to the appended drawings. Other datapackages generated and transmitted by the first portable communicationdevice, such as the third data package, may belong to the second packetcategory without audio data. Data packages belonging to the secondpacket category are preferably not retransmitted if a first transmissionattempt by the first or the second portable communication device failsbecause data of this packet category typically lack urgency (e.g. notreal-time critical) or may be uncritical to the proper operation of thefirst or second portable communication device. Hence, the data packagesbelonging to the second packet category may be deleted or flushed aftera failed first transmission attempt as discussed above. In thealternative, a failed first transmission attempt of a data packagebelonging to the second packet category may lead to a retransmissionattempt of a predetermined portion of the data package in question, forexample a payload section, at a later time instant. This later timeinstant may be during a later connection event. The first data packagemay comprise an optional default setting of the acknowledgementindicator since there is no previous data package to the first datapackage of a given connection event. However, to keep a coherent layoutof the first, second, third data packages, it may be desirable toinclude the acknowledgement indicator in the first data package and justignore its setting in the second portable communication device.

The maximum number of retransmission of a data package of the firstpacket category is limited to either the positive integer N or thepositive integer M depending on the communication device in question.Each of M and N is preferably at least 1 and at the most 4. Hence, thefirst data package may be retransmitted one, two, three or four timesand the second data package may be retransmitted one, two, three or fourtimes if the first or second data packages belong to the first packetcategory. In some embodiments of the present methodology, N may be equalto M. A data package of the first packet category is accordinglytransmitted at the most N+1 times or M+1 times, i.e. a failed firsttransmission attempt followed by at the most N or M retransmissionattempts. In this manner after each retransmission attempt of the firstdata package in response to a preceding failed transmission orretransmission attempt, the first portable communication device ismonitoring the wireless communication channel for the second datapackage transmitted by the second portable communication device for thepurpose of finding express receipt acknowledgement of the first datapackage. The third data package may belong to the second packet categoryfor the reasons discussed below. The first portable communication devicetherefore checks the setting of the acknowledgement indicator of thereceived second data package and if the acknowledgement indicator isunset or if the second data package is absent at an expected arrivaltime, the first portable communication device concludes that theretransmission attempt in question of the first data package is afailure and proceeds by making a further retransmission attempt of thefirst data package unless the maximum number N of retransmissions isreached. If N retransmissions have been reached, the first portablecommunication device preferably proceeds to flush, delete or abandon thefirst data package since N failed retransmissions have now been carriedout. Alternatively, if the N retransmissions have not been reached, thefirst portable communication device reverts to making a furtherretransmission attempt of the first data package and thereafter proceedsto monitoring the wireless communication channel as described aboveawaiting an acknowledgment indicator from the second data package.Finally, if the acknowledgement indicator of the second data package isset, the first portable communication device concludes that theretransmission attempt in question of the first data package wassuccessful and interrupts any further retransmission attempts. In thelatter situation, the first portable communication device may proceed byswitching certain wireless communication circuitry and functions to apower down mode as discussed in further detail below with reference tothe appended drawings. The flushing or deletion of data packagesbelonging to the first packet category after N failed retransmissions orafter M failed retransmissions, as the case may be, is helpful to reducelatency or time delay of a received audio stream compiled from multiplereceived data packages of the first packet category either at the firstor at second portable communication device. The flushing of the faileddata package allows the portable communication device in question to adda more up-to-date or current audio frame to the new data packagetransmitted after the flushed data package. This flushing procedure inrespect of lost data packages with audio data avoids that audiotransmission through the wireless bi-directional communication channelis blocked or hung by a large number, in principle an infinite number,of retransmission attempts of a particular audio data package.

During some connection events, where the first transmission and the Nretransmissions of the first data package all failed, the third datapackage may not be transmitted because the first portable communicationdevice utilizes all available package transmission attempts forretransmission of the first data package as discussed in further detailbelow with reference to FIG. 5 and FIG. 7 of the appended drawings.However, the probability of each of the latter failed transmissionoutcomes is generally small and may be brought down to a small valuesuch as below 1.0%, or below 0.1%, by an appropriate setting of thevalue of N, or M. Thus, during multiple connection events, a third datapackage will likely be transmitted because either the first transmissionof the first data package was successful or one of the at the most Nretransmissions of the first data package was successful.

The present method may comprise terminating a current connection eventin response to a successful transmission of the first, second and thirddata packages in the current connection event. Hence, this terminationprocess allows the first portable communication device to transmit asingle audio frame to the second portable communication device with thefirst data package, and vice versa in respect of the second datapackage, in the current connection event and receive express or positivereceipt acknowledgement in respect of each of the first and second datapackages. The first and second portable communication devices may entertheir previously discussed power down modes in connection with thetermination of the current connection event to save power.

If the first transmission and N retransmissions of the first datapackage fail in a current connection event as discussed above, a fourthdata package may be the first data package of a subsequent connectionevent. Likewise, if the second data package belongs to the first packetcategory and the first transmission and M retransmissions of the seconddata package fail in a current connection event as discussed above, thefourth data package discussed above may be the second data package ofthe subsequent connection event.

At least some of the data packages generated and transmitted by thefirst portable communication device may comprise audio data or audioframes and these data packages therefore belongs to the first packetcategory. The first portable communication device may comprise thehearing instrument discussed above. On the other hand, the plurality ofdata packages generated and transmitted by the second portablecommunication device such as the second data package may lack audio dataand solely include various types of control data for aligning orsynchronizing the operation of the first and second portablecommunication devices as discussed in further detail below.

If the first data package belongs to the second category, i.e. lacksaudio data, and the second data package from the second portablecommunication device is absent or the acknowledgement indicator of thesecond data package unset, the method may comprise steps of:

-   -   flushing, deleting or abandoning the first data package where        the first data package belongs to the second packet category,    -   adding a section of data, for example the control data, of the        first data package to a subsequent data package of the first or        the second packet category for transmission during a subsequent        connection event to the current connection event. The data        section of the first data package may comprise, or be limited        to, the payload data of the first data package. Hence, the first        communication device, or a controller such as a communication        controller of the first communication device, may be configured        strip the payload data, such as the control data, from the first        data package and add these payload data to the subsequent data        package. In this manner, the payload data may reach the second        portable communication device albeit with a delay.

The header section of each of the first, second and third data packagesmay comprise a predetermined code or value (L) indicating the categoryof the data package. This feature will allow a receipt circuitry of theportable communication device such as the communication controller torapidly and efficiently, i.e. using a low amount of power/energy, todetermine which packet category a received data package belongs to byreading the predetermined code or value. Hence, the communicationcontroller may take appropriate action based on the predetermined codeas read which is discussed in further detail below with reference to theappended drawings.

Hence, one embodiment of the present method of exchanging data packagesmay comprise steps of:

-   -   evaluating the predetermined code or value (L) of at least the        first or the second data package,    -   retransmitting or discarding the first or the second data        package in accordance with the predetermined code or value (L).

Some embodiments of the present method of exchanging data packages maycomprise a step of checking the error-detection code of the first or thesecond data package before proceeding to evaluating the predeterminedcode or value (L) as discussed above in connection with the evaluationof the acknowledgement indicator. If the error-detection code indicatesthat the data of the first or the second data package is invalid, thedata package in question may be flushed or discarded without evaluatingits predetermined code or value.

Furthermore, the predetermined code may according to one embodimentpoint to, or indicate, an address or position of a data package ofeither packet category holding a particular type of payload data such asaudio data and/or control data. The predetermined code may point to astart address of e.g. the control data, audio data or other data contentof the data package. The presence of this pointer type of predeterminedcode leads to a compact format of the data packages, i.e. small size.The compact format is achieved because the data package structure maydispense with ordinary overhead codes, fields or bits in front of eachof the individual data sections to identify a beginning of each of thesedata sections. The pointer property of the predetermined code thereforeallows a communication controller of the portable communication deviceto jump directly to respective start addresses of the various dataportions of the received data packages and read the data contentthereof. This direct access to the relevant start addresses saves thecommunication controller from parsing or decoding all data bytes of thereceived data package to detect locations of the desired data portionsor fields of the data package as discussed in further detail below withreference to the appended drawings. Various layouts or designs of datapackages of the first category and layouts of data packages of thesecond category are discussed in further detail below with reference tothe appended drawings.

A second aspect of one or more embodiments described herein relates to awireless binaural hearing aid system configured to exchange datapackages over a bi-directional wireless communication channel. Thehearing aid system comprises a first hearing instrument comprising afirst radio transceiver and a second hearing instrument comprising asecond radio transceiver. The first hearing instrument comprises a firstcommunication controller coupled to the first radio frequencytransceiver and the second hearing instrument comprising a secondcommunication controller coupled to the second radio transceiver wherethe first communication controller is configured to:

-   -   generating a plurality of data packages over time,    -   transmitting the plurality of data packages from the first to        the second portable communication device through a plurality of        spaced apart frequency bands distributed across a predetermined        radio frequency range of the bi-directional wireless        communication channel,    -   receiving a plurality of data packages over time transmitted        from the second portable communication device,    -   computing, respective transmission quality estimators, such as        respective packet error ratios (PERs), of the plurality of        spaced apart frequency bands,    -   determining a favoured frequency band based on the detected        transmission quality estimators,    -   transmitting, from the first to the second portable        communication device, a first data package of the plurality of        data packages a first time on the favoured frequency band.

The skilled person will understand that the second communicationcontroller of the second hearing instrument may operate in acorresponding manner to the first communication controller of the firsthearing instrument. The exchange of data packages afforded by thepresent wireless binaural hearing aid system enables digital exchange ofnumerous types of useful data, such as real-time digital audio signalsor digital audio streams, signal processing parameters, control data,such as volume control settings, identification of signal processingprograms, etc.

Each of the first and second hearing instruments or hearing aids maycomprise:

an input transducer, such as one or several microphones, configured tooutput an audio signal based on a signal applied to the input transducerand representing sound,

a hearing loss processor configured to compensate a hearing loss of auser of the hearing aid and output a hearing loss compensated audiosignal. The hearing loss compensated audio signal may be adapted torestore loudness such that loudness of the applied signal as it wouldhave been perceived by a normal listener substantially matches theloudness of the hearing loss compensated signal as perceived by theuser. Each of the first and second hearing instruments or hearing aidsmay additionally comprise an output transducer, such as a receiver orloudspeaker, an implanted transducer, etc., configured to output anauditory output signal based on the hearing loss compensated audiosignal that can be received by the human auditory system, whereby theuser hears the sound. The input transducer may also comprise a telecoilthat converts a time-varying magnetic field at the telecoil into acorresponding varying analogue audio signal in which the instantaneousvoltage of the audio signal varies continuously with the varyingmagnetic field strength at the telecoil. Telecoils may be used toincrease the signal to noise ratio of speech from a speaker addressing anumber of people in a public place, e.g. in a church, an auditorium, atheatre, a cinema, etc., or through a public address systems, such as ina railway station, an airport, a shopping mall, etc. Speech from thespeaker is converted to a magnetic field with an induction loop system(also called “hearing loop”), and the telecoil is used to magneticallypick up the magnetically transmitted speech signal. The input transducermay further comprise at least two spaced apart microphones, and abeamformer configured for combining microphone output signals of the atleast two spaced apart microphones into a directional microphone signal.The input transducer may comprise one or more microphones and a telecoiland a switch, e.g. for selection of an omnidirectional microphonesignal, or a directional microphone signal, or a telecoil signal, eitheralone or in any combination, as the audio signal. Typically, theanalogue audio signal is made suitable for digital signal processing byconversion into a corresponding digital audio signal in ananalogue-to-digital converter whereby the amplitude of the analogueaudio signal is represented by a binary number. In this way, adiscrete-time and discrete-amplitude digital audio signal in the form ofa sequence of digital values represents the continuous-time andcontinuous-amplitude analogue audio signal. Throughout the presentdisclosure, the “audio signal” may be used to identify any analogue ordigital signal forming part of the signal path from the output of theinput transducer to an input of the hearing loss processor. Throughoutthe present disclosure, the “hearing loss compensated audio signal” maybe used to identify any analogue or digital signal forming part of thesignal path from the output of the hearing loss processor to an input ofthe output transducer possibly via a digital-to-analogue converter.

Each of the first and second radio transceivers may comprise both awireless transmitter and a wireless receiver. The transmitter andreceiver may share common circuitry and/or a single housing.Alternatively, the transmitter and receiver may share no circuitry, andthe wireless communication unit may comprise separate devices with thetransmitter and the receiver, respectively. Signal processing in each ofthe first and second portable communication device may be performed bydedicated hardware or may be performed in one or more signal processors,or performed in a combination of dedicated hardware and one or moresignal processors. Likewise, the operations performed by each of thefirst and second communication controllers may be performed by dedicatedhardware or may be performed in one or more processors, or performed ina combination of dedicated hardware and one or more processors. As usedherein, the terms “processor”, “signal processor”, “controller”,“system”, etc., are intended to refer to microprocessor or CPU-relatedentities, either hardware, a combination of hardware and software,software, or software in execution. For example, a “processor”, “signalprocessor”, “controller”, “system”, etc., may be, but is not limited tobeing, a process running on a processor, a processor, an object, anexecutable file, a thread of execution, and/or a program. By way ofillustration, the terms “processor”, “signal processor”, “controller”,“system”, etc., designate both an application running on a processor anda hardware processor. One or more “processors”, “signal processors”,“controllers”, “systems” and the like, or any combination hereof, mayreside within a process and/or thread of execution, and one or more“processors”, “signal processors”, “controllers”, “systems”, etc., orany combination hereof, may be localized on one hardware processor,possibly in combination with other hardware circuitry, and/ordistributed between two or more hardware processors, possibly incombination with other hardware circuitry. Also, a processor (or similarterms) may be any component or any combination of components that iscapable of performing signal processing. For examples, the signalprocessor may be an ASIC processor, a FPGA processor, a general purposeprocessor, a microprocessor, a circuit component, or an integratedcircuit.

A method of exchanging data packages between a first portablecommunication device and a second portable communication device over abi-directional wireless communication channel, where at least one of thefirst and second portable communication devices comprises a hearinginstrument, includes: generating, by the first portable communicationdevice, a first plurality of data packages; transmitting the firstplurality of data packages from the first portable communication deviceto the second portable communication device through a plurality ofspaced apart frequency bands distributed across a radio frequency rangeof the bi-directional wireless communication channel; computing, at thefirst wireless communication device or at the second wirelesscommunication device, transmission quality estimators for the respectivespaced apart frequency bands; determining a favoured frequency bandbased on the transmission quality estimators; and transmitting, from thefirst portable communication device to the second portable communicationdevice, a second plurality of data packages on the favoured frequencyband, the second plurality of data packages comprising a first datapackage.

Optionally, the method further includes receiving a second data packagetransmitted from the second portable communication device to the firstportable communication device on the favoured frequency band.

Optionally, the method further includes establishing a plurality ofsuccessive connection events through the bi-directional wirelesscommunication channel; wherein the second plurality of data packages istransmitted during at least a subset of the plurality of successiveconnection events on the favoured frequency band.

Optionally, one of the second plurality of data packages comprises aheader section, a payload section, and a data check section holding apackage error-detection code.

Optionally, the method further includes adding a band identifierindicating the favoured frequency band to a predetermined header fieldof the header section.

Optionally, a first subset of the second plurality of data packagestransmitted by the first portable communication device belongs to afirst packet category comprising audio data, and a second subset of thesecond plurality of data packages belongs to a second packet categorywithout audio data.

Optionally, a size of the data packages in the second subset belongingto the second packet category is smaller than a size of the datapackages in the first subset belonging to the first packet category.

Optionally, if the transmission of one of the second plurality of datapackages fails, the method further comprises retransmitting the one ofthe second plurality of data packages for at most N times if the one ofthe second plurality of data packages belongs to the first packetcategory; wherein N is a positive integer between 1 and 4.

Optionally, if the transmission of one of the second plurality of datapackages fails, the method further comprises: selecting, in accordancewith a frequency hopping key, a frequency band of the plurality ofspaced apart frequency bands that is different from the favouredfrequency band; and retransmitting the one of the second plurality ofdata packages on the different frequency band.

Optionally, the method further includes adding a first plurality ofacknowledgement indicators, at the first portable communication device,to the first plurality of data packages before they are transmitted bythe first portable communication device, wherein at least a subset ofthe first plurality of acknowledgement indicators indicates whether aprevious data package was successfully received at the first portablecommunication device.

Optionally, the method further includes adding a second plurality ofacknowledgement indicators, at the second portable communication device,to a third plurality of data packages before they are transmitted by thesecond portable communication device, wherein at least a subset of thesecond plurality of acknowledgement indicators indicates whether aprevious data package was successfully received at the second portablecommunication device.

Optionally, the method further includes receiving a second data packageat the first portable communication device; wherein if anacknowledgement indicator of the second data package is set: the methodfurther comprises generating, at the first portable communicationdevice, a third data package comprising an acknowledgment indicatorsetting reflecting successful or failed receipt of the second datapackage, and transmitting the third data package to the second portablecommunication device.

Optionally, if the first portable communication device fails to receivea second data package or if an acknowledgement indicator of the seconddata package is unset: the method further comprises setting anacknowledgment indicator of one of the second plurality of data packagesto reflect a failed receipt of the second data package, andretransmitting the one of the second plurality of data packages from thefirst portable communication device to the second portable communicationdevice.

Optionally, act of retransmitting the one of the second plurality ofdata packages is performed if the one of the second plurality of datapackages belongs to the first packet category.

Optionally, the method further includes: receiving a second data packageat the first portable communication device; and checking anerror-detection code of the second data package subsequent to receipt ofthe second data package at the first portable communication device;wherein if the error-detection code indicates invalid data of the seconddata package, the method further comprises ignoring a setting of anacknowledgment indicator of the second data package, and unsetting anacknowledgment indicator of a third data package to reflect a failedreceipt of the second data package.

Optionally, the method further includes: generating, by the secondportable communication device, a second data package with anacknowledgment indicator setting reflecting successful or failed receiptof one of the first or second plurality of data packages; andtransmitting the second data package from the second portablecommunication device to the first portable communication device throughthe bi-directional wireless communication channel.

A wireless binaural hearing aid system configured to exchange datapackages over a bi-directional wireless communication channel, includes:a first hearing instrument comprising a first radio transceiver and afirst communication controller coupled to the first radio frequencytransceiver; and a second hearing instrument comprising a second radiotransceiver and a second communication controller coupled to the secondradio transceiver; wherein the first communication controller isconfigured for: generating a first plurality of data packages,transmitting the first plurality of data packages for reception by thesecond hearing instrument through a plurality of spaced apart frequencybands distributed across a radio frequency range of the bi-directionalwireless communication channel, computing transmission qualityestimators for the respective spaced apart frequency bands, determininga favoured frequency band based on the transmission quality estimators,and transmitting a second plurality of data packages on the favouredfrequency band for reception by the second hearing instrument, thesecond plurality of data packages comprising a first data package.

Other aspects and features will be evident from reading the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the embodiments are described in more detail withreference to the appended drawings, wherein

FIG. 1 schematically illustrates a wireless binaural hearing aid systemin accordance with a first embodiment, where the system comprises afirst hearing instrument and a second hearing instrument connected via abi-directional wireless communication channel,

FIG. 1A) schematically illustrates a wireless hearing aid system inaccordance with a second embodiment, where the system comprises a firsthearing instrument and a portable communication device connected via abi-directional wireless communication channel,

FIG. 2 schematically illustrates exemplary data package layouts for datapackages transmitted between portable devices of the wireless hearingaid system or the wireless binaural hearing aid system,

FIG. 3 shows a schematic time-frequency diagram of a first exemplarytransmission of data packages between the first and second hearinginstruments in accordance with some embodiments,

FIG. 4 shows a schematic time-frequency diagram of a second exemplarytransmission of data packages between the first and second hearinginstruments in accordance with some embodiments,

FIG. 5 shows a schematic time-frequency diagram of a third exemplarytransmission of data packages of different categories between the firstand second hearing instruments in accordance with some embodiments,

FIG. 6 shows a schematic time-frequency diagram of a fourth exemplarytransmission of data packages of different categories between the firstand second hearing instruments in accordance with some embodiments; and

FIG. 7 shows a schematic time-frequency diagram of a fifth exemplarytransmission of data packages of different between the first and secondhearing instruments in accordance with some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

Various embodiments are described hereinafter with reference to thefigures. Like reference numerals refer to like elements throughout. Likeelements will, thus, not be described in detail with respect to thedescription of each figure. It should also be noted that the figures areonly intended to facilitate the description of the embodiments. They arenot intended as an exhaustive description of the claimed invention or asa limitation on the scope of the claimed invention. In addition, anillustrated embodiment needs not have all the aspects or advantagesshown. An aspect or an advantage described in conjunction with aparticular embodiment is not necessarily limited to that embodiment andcan be practiced in any other embodiments even if not so illustrated, orif not so explicitly described.

In the following various exemplary embodiments of the presentmethodology of exchanging data packages between a first portablecommunication device and a second portable communication device over abi-directional wireless communication channel are described withreference to the appended drawings. At least one of the first and secondportable communication devices comprises a hearing instrument asdiscussed in additional detail below.

FIG. 1 schematically illustrates a wireless binaural hearing aid systemcomprising a left ear hearing aid or instrument 10L and a right earhearing aid or instrument 10R, each of which comprises a wirelesscommunication unit for connection to the other hearing instrument oralternatively another audio-enabled portable communication device suchas a smartphone or mobile phone, an audio-enabled tablet, a cordlessphone, a TV-set, a portable microphone array etc. In the presentembodiment, the left ear and right ear hearing aids 10L, 10R areconnected to each other via a bi-directional wireless communicationchannel or link 12. A unique ID may be associated with each of the leftear and right ear hearing aids 10L, 10R. The illustrated binauralhearing aid system may be configured to operate in the 2.4 GHzindustrial scientific medical (ISM) band and may comprise between 60 and120 spaced apart frequency bands or channels. Each of the spaced apartfrequency bands or channels may possess a bandwidth between 0.5-2.0 MHzsuch as about 1.0 MHz.

The left hearing aid 10L and the right hearing aid 10R may besubstantially identical in some embodiments expect for theabove-described unique ID such that the following description of thefeatures of the left hearing aid 10L also applies to the right hearingaid 10R. The left hearing aid 10L may comprise a ZnO₂ battery (notshown) that is connected for supplying power to the hearing aid circuit14. The left hearing aid 10L comprises an input transducer in the formof a microphone 16. The microphone 16 outputs an analogue or digitalaudio signal based on an acoustic sound signal arriving at themicrophone 16 when the left hearing aid 10L is operating. If themicrophone 16 outputs an analogue audio signal the hearing aid circuit14 may comprise an analogue-to-digital converter (not shown) whichconverts the analogue audio signal into a corresponding digital audiosignal for digital signal processing in the hearing aid circuit 14. Inparticular in a hearing loss processor 24L that is configured tocompensate a hearing loss of a user of the left hearing aid 10.Preferably, the hearing loss processor 24L comprises a dynamic rangecompressor well-known in the art for compensation of frequency dependentloss of dynamic range of the user often termed recruitment in the art.Accordingly, the hearing loss processor 24L outputs a hearing losscompensated audio signal to a loudspeaker or receiver 32L. Theloudspeaker or receiver 32 converts the hearing loss compensated audiosignal into a corresponding acoustic signal for transmission towards aneardrum of the user. Consequently, the user hears the sound arriving atthe microphone; however, compensated for the user's individual hearingloss. The hearing aid may be configured to restore loudness, such thatloudness of the hearing loss compensated signal as perceived by the userwearing the hearing aid 10 substantially matches the loudness of theacoustic sound signal arriving at the microphone 16 as it would havebeen perceived by a listener with normal hearing.

The hearing aid circuit 14 further includes a wireless communicationunit which comprises a radio portion or transceiver 34L that isconfigured to communicate wirelessly with the right or second hearingaid 10R. The wireless communication unit comprises a first communicationcontroller 26L performing various communication protocol related tasksand possibly other tasks. The hearing loss processor 24L may comprise asoftware programmable microprocessor such as a Digital Signal Processor.The operation of the left hearing aid 10L may be controlled by asuitable operating system executed on the software programmablemicroprocessor. The operating system may be configured to manage hearingaid hardware and software resources, e.g. including the hearing lossprocessor 24L and possibly other processors and associated signalprocessing algorithms, the wireless communication unit, certain memoryresources etc. The operating system may schedule tasks for efficient useof the hearing aid resources and may further include accounting softwarefor cost allocation, including power consumption, processor time, memorylocations, wireless transmissions, and other resources. The operatingsystem controls in cooperation with the first communication controller26L the radio transceiver 34L to perform the bi-directional wirelesscommunication with the right or second hearing aid 10R in accordancewith the present methodology or protocol for exchange of data packages.The right or left hearing aid may operate as a master device and theother hearing aid as a slave in connection with bi-directional datacommunication between the hearing aids.

The data packages generated and transmitted by the each of the lefthearing aid 10L and right hearing aid 10R may comprise audio data suchthat each hearing aid may receive and deliver a binaurally processedhearing loss compensated audio signal to the user or patient via therespective loudspeakers or receivers 32L, 32R. Alternatively, only datapackages generated and transmitted by single one of the left and righthearing aids 10L, 10R comprises the audio data, such as real time audiodata or audio samples, while the other hearing aid solely transmits datapackages with various kind of control information or data for example tosynchronize operation between the left and right hearing aids 10L, 10R.Hence, according to this latter embodiment only one of the left andright hearing aids performs binaural processing of the hearing losscompensated audio signal. This processing scheme is often utilized inso-called CROSS hearing aid systems.

FIG. 2 schematically illustrates four exemplary data packages 200 a, 200b, 200 c, 200 d of different types transmitted between the left andright hearing aids 10L, 10R of the wireless binaural hearing aid system50. The features and layout of each of these types of data packages 200a, 200 b, 200 c, 200 d are discussed in detail below.

FIG. 3 is a schematic time-frequency diagram or plot of a firstexemplary transmission of data packages P1, P2, P3, P4, P5 of differentcategories between the left and right hearing aids 10L, 10R inaccordance with various embodiments. The illustrated first exemplarytransmission of data packages will typically correspond to environmentalconditions with low levels of interfering electromagnetic noise in theutilized frequency band or bands such that transmission of each datapackage may be successful at the first transmission attempt or firsttransmission. In the latter situation there is no need forretransmission of the data packages. However, the present data packagetransmission methodology and protocol for exchange of data packages aredesigned to cope with a significant error rate in the transmitted datapackages. This feature is particularly helpful for data packagetransmission in wireless binaural hearing instrument systems where theshadowing effect of the user's head often leads to a relatively highpacket error rate (PER). The data package transmission methodology mayenable retransmission of lost data packages of a first packet categorywith audio data. The number of retransmission of a data package of thefirst packet category may be limited to a certain maximum number oftimes such as between 1 and 4 times (e.g., 1 time, 2 times, 3 times, or4 times). The loss of data packages may occur for numerous reasons suchas air collisions with other radio frequency traffic in the utilizedfrequency band. There are several noticeable advantages of applying thistype of limitation to the number of retransmissions of a particular datapackage of the first packet category such as limiting consumedtransmission energy per transmitted audio frame and provide an upperbound on package transmission latency. The package transmission latencyis an important feature of the transmission methodology or protocol ifthe respective audio data or frames of the data packages represent realtime audio signals of the left and/or right hearing aids 10L, 10R. Theloss of audio frames from time to time when a particular data packagehas been unsuccessfully retransmitted the maximum number of times, e.g.4 times, may be mitigated by adding a suitable audio codec to thehearing aid circuit 14L, 14R. The audio codec may be able to handle acertain amount of audio frame loss of an incoming real time audio datastream from the first or second communication controller 26L, 26R. Theaudio codec may for example be configured to execute a Packet LossConcealment algorithm to perceptually mask the lost audio frames ofincoming real time audio data stream.

A connection between the left and right hearing aids 10L, 10R needs tobe established prior to exchanging the data packages. This connectionmay be permanent or intermittent during the operation of the left andright hearing aids 10L, 10R. To initialize or establish the connection,the left hearing aid 10L may be configured as Master (M) device and theright hearing aid 10R as a Slave (S) device in accordance with theBluetooth LE protocol. Consequently, in accordance with the Bluetooth LEprotocol the slave hearing aid 10R may start to transmit advertisingmessages at constant time intervals on the three frequency bands in arandom sequence, and listen for connect requests from the master hearingaid 10L. Once the slave hearing aid 10R receives a connect request fromthe master hearing aid 10L, the slave hearing aid 10R may be adapted toconfigure itself with a number of connection parameters provided by themaster hearing aid 10L. The slave hearing aid 10R may thereafter startlistening, i.e. monitoring the bi-directional wireless communicationchannel, for the data packages transmitted by the master hearing aid 10Rat a time interval determined by the provided connection parameters.Similarly, during the connection phase, the master hearing aid 10L maylisten for the advertising messages randomly on the three designatedfrequency channels for a short time period. If no connection has beenestablished for the given time period, it may be assumed that there isno remote hearing instrument available and the connection initializationprocess or protocol may be terminated. The connection parameters mayinclude one or more of: transmission interval, payload size, channeldata rate, hopping key or scheme, maximum number of packageretransmissions N, etc.

As shown on the schematic time-frequency diagram 300 of FIG. 3, thefirst exemplary transmission of data packages P1, P2, P3, P4 and P5 usesan intermittent data exchange scheme comprising a plurality ofsuccessive connection events of a predetermined duration for theexchange of the data packages. Consecutive connection events on thebi-directional wireless communication channel 12 are indicated by Ci1,Ci2, Ci3, etc. along time axis t. The skilled person will understandthat the illustrated adjacent connection events such as Ci1 and Ci2 maybe separated in time by disconnect time periods/idle time periods 320.The time separation, or transmission interval, between a pair ofadjacent connection events such as Ci1 and Ci2 or Ci2 and Ci3 etc. maylie between 2 ms and 20 ms such as between 5 ms and 10 ms. The durationof the connection events Ci1, Ci2, Ci3 etc. will generally vary overtime depending on the required number of retransmissions of the firstand/or second data packages P1, P2, the channel data rate and the sizeof the data packages. The channel data rate may be placed between 0.5Mbit/s and 2 Mbit/s. The duration of each of the successive connectionevents may for example lie between 0.5 ms and 5 ms such as between 0.9ms and 2.5 ms. In the latter case, this may correspond to a firstcategory data package size of 30 bytes with a maximum number ofretransmissions set to N=3. Furthermore, the transmission protocolaccording to one or more embodiments described herein attempts to, ineach connection event, successfully transmit a single data package withaudio data from left to the right hearing aid and vice versa. Hence,once each of the left and right hearing aids 10L, 10R has successfullytransmitted its data package during a particular connection event, thehearing aid in question may switch to an idle or low-power modeassociated with the idle time periods 320. During the idle mode, theradio transceiver 34L of the left hearing aid 10L and the radiotransceiver 34R of the left hearing aid may be powered down to reducepower consumption of the respective hearing aids. The skilled personwill understand that the bi-directional wireless communication channel12 may be permanently connected in other embodiments, i.e. without theidle time periods 320 between successive connection events.

The y-axis of schematic time-frequency diagram 300 indicates thefrequency band number, n, of the previously discussed plurality ofspaced apart frequency bands or channels of the bi-directional wirelesscommunication channel. As illustrated by the schematic time-frequencydiagram 300, the present embodiment of the methodology of exchangingdata packages comprises steps of adding an acknowledgement indicator toeach of the transmitted data packages P1, P2, P3, P4 and P5. Theacknowledgement indicator is preferably added to a particular field orbit of a header section (refer to 203 of FIG. 2) of each of thetransmitted data packages. A set/asserted acknowledgement indicator isillustrated by a hatched field 303 of the data package while an unsetacknowledgement indicator is illustrated by a blank field 303. A setacknowledgement indicator of a particular data package such as P2indicates that a previously transmitted data package to P2 by the samehearing aid was correctly received at the left or right hearinginstrument as the case may be. Consequently, the assertedacknowledgement indicator of P2 indicates that the previous data packageP1, transmitted by the left hearing aid 10L, was correctly received atthe right hearing aid 10R. Likewise, the asserted acknowledgementindicator of a data package P3, transmitted by the right hearing aid 10Rthrough the wireless communication channel subsequently to its receiptof P2, indicates that P2 was correctly received at the left hearing aid10L. The settings of the acknowledgement indicators of the transmitteddata packages such as P1, P2, P3 etc. may be carried out by therespective communication controllers 26L, 26R (please refer to FIG. 1)of the left and right hearing aids. Each of the communication controller26L, 26R may be configured to access and manipulate the relevant fieldor bit (refer to item 203 of FIG. 2) of the header section of each ofthe data packages as required before transmission of the data package inquestion.

During the first connection event Ci1 through the wireless communicationchannel 12 between the left and right hearing instruments, thecommunication controller 26L is generating the first data package P1 byidentifying, retrieving and adding the necessary data bits or bytes tothe appropriate fields or positions of the selected type or category ofdata package. Several types of data packages 200 a, 200 b, 200 c, 200 dwith differing data content may exist as illustrated on FIG. 2. Thefirst and second types of data packages 200 a, 200 b comprise audio dataand therefore belong to the first packet category. The third and fourthtypes of data packages 200 c, 200 d lack audio data and therefore belongto the second packet category. The first type of data package 200 a hastypically a larger size than the second type data package 200 b due tothe lack of control data in the later type of data package. However, thesize of the second type of data package 200 b of the first packetcategory may be at least two times larger than the largest one of thethird and fourth types of data packages 200 c, 200 d belonging to thefirst packet category.

In the present embodiment, the first data package P1 belongs to thepreviously discussed first packet category for example the data packagetype 200 a or data package type 200 b, schematically illustrated on FIG.2, which are distinct from a second data packet category by theircontent of audio data. The audio data is held in a payload section orportion 211 of the data package types 200 a or 200 b. The payloadsection of the data package type 200 b contains exclusively audio datawhile the payload section of the data package type 200 a in contrastcontains at least audio data and control data. In both types of datapackages 200 a and 200 b, the audio data typically comprises an audioframe which may have a size corresponding to between 2 ms and 5 ms of areal-time audio data stream. The audio data portion 211 of the payloadsection may comprise between 10 and 40 bytes of audio data. The speed ofthe underlying real-time audio stream may lie between 16 kbit/s and 96kbit/s such as between 32 kbit/s and 48 kbit/s.

In connection with the generation of the first data package P1, theacknowledgement indicator 303 of P1 is unset by the communicationcontroller 26L by default before transmission to the right hearinginstrument via the radio transceiver 34L and the RF antenna 44L. Since,P1 is the first data package in the connection event there exist noprevious data package for which to acknowledge receipt. In the right orslave hearing aid 10R, the communication controller 26R is configured tomonitoring the wireless communication channel 12 for receipt of thefirst data package P1. The first data package P1 is expected at aparticular time window as discussed in further detail below. If and onceP1 is received at the right hearing aid 10R (S), the associatedcommunication controller 26R checks the data content of P1 based on apriori knowledge of the layout of the first and second categories ofdata packages 200 a, 200 b, 200 c, 200 d of the communication protocol.This check includes a check of an error-detecting code, such as CRC, inan error code section 213 of P1. The error-detecting code indicateswhether or not the data content of P1 is corrupted or invalid. Assumingthe CRC check shows that the data held in P1 is valid or uncorrupted,the communication controller 26R generally evaluates the setting of theacknowledgement indicator 303 of P1 by reading the relevant bit field ofthe header section of P1. The communication controller 26R may, however,ignore the setting of the acknowledgement indicator 303 of P1 one timeat the first attempt to transmit a new data package P2. This is becausethis is the first attempt to transmit this data package P2 during thefirst connection event Ci1 such that the success or failure of aprevious transmission of P2 is irrelevant. The communication controller26R is preferably configured to evaluate and respond to the setting ofthe acknowledgement indicator of each data package received from theleft hearing aid after the first attempt transmission of P1—for examplethe acknowledgement indicator of P3 in the present example. These laterdata packages may be retransmitted versions of P1 in other examples. Ifthe acknowledgement indicator of a such as later data package is set orasserted, the communication controller 26R is informed that thepreviously transmitted data package by the right hearing aid 10R wascorrectly received at the left or master hearing aid 10L. Consequently,no re-transmission of this previous data package is needed or carriedout by the right hearing instrument 10R no matter of the actual packetcategory of this previous data package. The new data package P2 maycomprise a new audio frame relative to the audio data of a previous datapackage transmitted by right hearing aid 10R during the connection eventprevious to Ci1. The skilled person will appreciate that these audioframes of the previous data package and the audio frame of P2 may beadjacent segments of a real-time audio stream derived from a microphonesignal of the right hearing aid.

If the above-mentioned CRC check of the received data package P1indicates valid or uncorrupted data, the communication controller 26Rproceeds to set the acknowledgement indicator 303 of P2 in connectionwith the generation of the data content of P2. Thereafter, thecommunication controller 26R proceeds to transmit P2 to the left hearingaid 10L via the radio transceiver 34R and the RF antenna 44R. There is atime gap or separation 313 between the transmission of P1 and thetransmission of P2 which is designated an “inter-frame spacing” which isthe time from a last transmitted bit of P1 to a first received bit in P2or for any pair of successive data packages in a particular connectionevent. This inter-frame spacing may line between 25 μs and 300 μs suchas between 40 μs and 200 ρs.

On the other hand in case the communication controller 26R finds that P1is absent at the expected time window or the CRC check of P1 failed, thecommunication controller 26R concludes that the first attempttransmission of P1 was a failure and proceeds to unset theacknowledgement indicator 303 of P2 in connection with the generation ofthe data content of P2. Thereafter, the communication controller 26Lproceeds to transmit P2 to the left hearing aid 10L as outlined above.

The communication controller 26L of the left hearing aid 10L is nowmonitoring the wireless communication channel 12 for receipt of thesecond data package P2 in a corresponding manner to the one discussedabove in respect of the communication controller 26R of the righthearing aid 10R. Once P2 is received at the left hearing aid 10L via itsradio transceiver 34L and the RF antenna 44L, the associatedcommunication controller 26L checks the data of P2 in a similar manneras discussed above in respect of P1. If the CRC check shows uncorrupteddata package content of P2, the communication controller 26L evaluatesthe setting of the acknowledgement indicator 303 as discussed above inrespect of P1. If the acknowledgement indicator 303 of P2 is set orasserted, as indicated by the hatched bit field 303 of P2, thecommunication controller 26L concludes the previously transmitted datapackage, P1, by the left hearing aid 10L was correctly received at theright hearing aid 10R. Consequently, the communication controller 26Lfinds or concludes that retransmission of P1 is unnecessary independentof the actual packet category of P1. Hence, the communication controller26L generates in response to the latter finding (i.e. P1 was correctlyreceived), a new data package P3. The new data package P3 is preferablytransmitted on another frequency band than P1 and P2 for example aparticular predetermined frequency band such as frequency band No. 1 asillustrated on the plot 300. This feature is discussed in further detailbelow. Furthermore, since each of the communication controllers 26L, 26Rof the left and right hearing aids now has transmitted the intendedsingle data package comprising associated audio data, the data packageP3 does not include audio data and therefore belongs to the secondpacket category. The purpose of transmitting P3 is to inform thecommunication controller 26R/microprocessor of the right hearing aid 10Rthat its earlier transmitted data package P2 was actually successfullyreceived at the left hearing aid 10L. On the other hand, if the firstattempt to transmit P2 was unsuccessful or failure because P2 was eithernot received at the left hearing aid 10L or had corrupted data asindicated by a failed CRC check, the communication controller 26Lresponds by un-setting the acknowledgement indicator of P3. Afterreceipt and evaluation of this P3 package, the communication controller26R responds by retransmitting P2 for a limited number of times anddiscussed in further detail below with reference to FIG. 4. In thepresent embodiment, the new data package P3 belongs in either case toanother packet category, e.g. second category without audio data, thanthe first and second data packages P1 and P2. The latter data packagesboth belong to the first packet category with audio data as illustratedby the exemplary data package layouts 200 a and 200 b depicted on FIG.2. Each of the first and second data packages P1 and P2 may have agreater length or size than P3. The layout of P3 may be similar toeither the exemplary data package 200 c or the exemplary data package200 d of FIG. 2 since both of these data packages 200 c, 200 d belong tothe second packet category lacking audio data. Hence, the size of P3 maybe markedly smaller than the size of P1 and P2 such that the generationand transmission of P3 consume significantly less power than thegeneration and transmission of the first data package P1 or P2. The sizeor length of each of data packages P1 and P2 may lie between 20 bytesand 50 bytes while the size of P3 may less than half of that size. Thecontent of P3 may be limited to the header section only as illustratedby the exemplary data package layout 200 c of FIG. 2. This headersection includes the appropriate bit field for the acknowledgementindicator 203 of P3 allowing P3 to function as a power efficientacknowledgement indicator confirming to the left hearing aid correctreceipt at the right hearing aid of the previous data package P2. Hence,the size of a data package of the first category may be at least twotimes the size of a data package of the second category in someembodiments of the present methodology. The present embodiment of thedata package transmission methodology involves the generation andtransmission of data packages of different sizes within at least some ofthe successive connection events Ci1, Ci2, Ci3 etc. These differentlysized data packages may belong to at least two distinct categories ofwhich a first category includes data packages which comprises audioframes or audio data while a second category includes data packageswhich lack audio frames or audio data. The skilled person willunderstand that other embodiments may use data packages of constant sizesuch that P3 has the same size as P1 and P2. Once the communicationcontroller 26L/microprocessor of the left hearing aid 10L hassuccessfully received P3 and found the acknowledgement indicator set,the communication controller 26L/microprocessor can conclude that theearlier transmitted data package P2 was successfully received at theright hearing aid 10RL. Hence, the communication controllers 26L, 26R ofthe left and right hearing aids, respectively, can conclude that allpending data packages with audio frames, i.e. P1 and P2, have beensuccessfully transmitted to the other hearing aid in the currentconnection event Ci1. Hence, the communication controllers 26L, 26Rpreferably switches the respective the radio transceivers 34L, 34R, andpossibly other circuitry involved in the bi-directional wirelessinterface handling, to an idle or low-power mode to save power. Thecommunication controllers 26L, 26R may maintain these idle modes untilthe next connection event Ci2 is scheduled in accordance with thecurrently selected time separation between pairs of successiveconnection events. During these intermittent idle or power down periods320, the bi-directional communication channel 12 may reside in aphysically disconnected state, but logically connected state. At thesubsequent connection event Ci2, the communication controllers 26L, 26Rswitch the respective radio transceivers 34L, 34R back to theiroperational states and the left and right hearing aids initialize thepreviously described connecting procedure to be ready for the generationand exchange of the subsequent data packages P4, P5 and P6 in a similarmanner as described above in respect of P1, P2 and P3. Consequently,data packages P4, P5 and P6 may be viewed as a first data package, asecond data package and a third data package, respectively, of thesubsequent connection event Ci2 and so forth for each of the successiveconnection events Ci3, CiN etc.

The bi-directional wireless communication channel preferably comprisesthe previously discussed plurality of spaced apart frequency bands orchannels, n, as discussed above. Different embodiments of the presentmethodology of exchanging data packages utilize different ways ofdistributing the transmitted data packages over the plurality of spacedapart frequency bands, i.e. different frequency hopping schemes. In someembodiments the first, second, third and any further data packages ofeach connection event are transmitted on different frequency bands ofthe plurality of spaced apart frequency bands. The different frequencybands may for example be selected in accordance with a predeterminedfrequency hopping key or algorithm. A relatively simple frequencyhopping scheme or key may be utilized where a random hopping key isgenerated by the master device of the left and right hearing aids, i.e.10L. The master/left hearing aid transmits the random hopping key to theright hearing aid 10R which is configured as slave device in the presentembodiment. The random hopping key may be transmitted to the slave/righthearing aid 10R as part of the previously discussed transmission ofconnection parameters during initialization of a connection event. Eachof the left and right hearing aids may thereafter use this randomhopping key to select the appropriate frequency band to transmit andreceive a particular data package on. The next frequency band of theplurality of spaced apart frequency bands may be selected as thepreviously used frequency band plus the hopping key. If the computedfrequency band exceeds the number of available frequency bands, amodulus operation is preferably applied to the hopping key to determineor compute a frequency band within the available number of frequencybands. A new frequency band may for example be selected for each datapackage transmission to avoid a data package is retransmitted on acongested frequency band. FIG. 7 shows a schematic time-frequencydiagram or plot of the transmission of data packages P1, P2, P3, P4 andP5 of different categories where the hopping key is set to 1 and themaximum number of retransmissions, N, is set to 2. Please note how thestart frequency band for the next data package is synchronized to aknown value at the first transmission of a data package in a newconnection event such as Ci2. In this case, the start frequency band forthe data package P3 of Ci2 is equal to the frequency band of theprevious package, i.e. last transmission of P2 in the previousconnection event Ci1, plus the hopping key, which is one in the presentexample as illustrated by dotted line 714. Hence, the frequency band fortransmission of the data package P3 is band No. 6 where the lasttransmission of P2 was performed plus one which gives frequency band No.7.

The frequency hopping key or scheme may be given by the followingequation:f _(n+1)=(f _(n) +h) % p; wheref_(n) represents the frequency band at time instant n;h represents the hopping key and n, h>=0 and positive integers;% represents the modulus operator;p is the number of spaced apart frequency bands.

The modulus value, %, may be selected to a prime number closest to thenumber of utilized frequency bands for example between 60 and 120. Ifthe number of frequency bands is set to 78 the modulus value mayaccordingly be set to the closest prime number to 78 which is 79. Theuse of a prime number is preferable because it provides a gooddistribution of the transmitted data packages across the number ofavailable frequency bands.

In an alternative embodiment of the frequency hopping scheme involvesthe determination of a favoured or “golden” frequency band amongst theplurality of spaced apart frequency bands. This embodiment of thefrequency hopping scheme is for example utilized in the exemplary datapackage transmission sequence illustrated on FIG. 3 where frequency bandor channel No. 5 is chosen as the favoured or “golden” frequency band.According to the latter embodiment, the methodology of exchanging datapackages comprises steps of detecting, at the right hearing aid and/orleft hearing aid, respective transmission quality estimators such asrespective packet error ratios (PERs) of the plurality of spaced apartfrequency bands and determining the favoured frequency band based on aplurality of detected transmission quality estimators. At least thefirst and second data packages, i.e. P1 and P2 for connection event Ci1,are transmitted a first time on the favoured frequency band within aparticular connection event. There are numerous benefits of using thefavoured or “golden” frequency band in the first attempt to send thefirst and second data packages if the frequency band with the lowest PERis selected as the favoured frequency band. The low PER of the favouredfrequency band maximizes the likelihood of a successful first attempttransmission of one of both of the first and second data packagesthereby reducing audio frame latency. This favoured frequency bandscheme also minimizes the required power consumption for a successfultransmission of the first and second data packages because the number ofretransmissions of data packages is minimized in a statistical sense.Furthermore, the likelihood of a data package of the first categoryneeds to be flushed or abandoned following N unsuccessfulretransmissions is reduced leading to a reduced loss of audio frames atthe receiving hearing aid. This feature leads to better sound quality ofthe received audio stream and lower power consumption of a possiblepackage loss concealment algorithm running in the processor of the leftor right ear hear hearing instrument. As illustrated on FIG. 3, wherefrequency band No. 5 is the favoured frequency band, the first andsecond data packages are transmitted a first time on that frequencyband. The third data package P3 may be transmitted a first time on thefavoured frequency band or another default frequency band such asfrequency band No. 1 as illustrated. It may be advantageous to chooseanother frequency band than the favoured frequency band as illustratedfor the first transmission of the data package P3 to get a valid or goodstatistical estimate of the PER of each of the plurality of frequencybands even when the favoured frequency band possesses favourabletransmission quality. To compute a valid PER statistic for a particularfrequency band there obviously needs to be a certain amount of datapackage traffic on the frequency band. During the second connectionevent Ci2, the new data packages P4 and P5 are likewise transmitted fora first time on the favoured frequency band No. 5 and the same scheme ispreferably applied to the first attempt to transmit the first and seconddata packages of each of the further connection events. However, thesixth data package P6 is not transmitted on the favoured frequency bandNo. 5 in the second connection event Ci2, but on frequency band No. 4 inaccordance with the chosen hopping key of one and the fact that the lastdata package of the previous connection event Ci1 was P3 on frequencyband No. 3.

The communication controller 26L/microprocessor of the master hearingaid, i.e. the left hearing aid, may be configured to compute therespective PERs of the plurality of spaced apart frequency bands anddetermine the favoured frequency band based on a the computed PERs. Theskilled person will understand that the communication controller 26L maycompute a running estimate over time of the plurality of detectedtransmission quality estimators such that the favoured frequency bandmay change from time to time in accordance with the smallest currentvalue of the running estimates of the PERs of the frequency bands. Thecommunication controller 26L of the master hearing aid may be configuredto adding a band identifier indicating the favoured or golden frequencyband to a predetermined header field of the header section of the datapackages generated and transmitted by the master hearing aid. Asillustrated on FIG. 2, the section of the header holding or storing thefavoured band identifier 207 may comprise 7 bits if 78 frequency bandsare utilized, but this header section may naturally comprise fewer bitsor more bits if less or more frequency bands are utilized.

FIG. 2 illustrates several exemplary types of data packages 200 a, 200b, 200 c, 200 d with differing data content that are utilized in thepresent methodology as discussed above. The data package types 200 a and200 b belong to the previously discussed first packet category whichincludes audio data for example audio frames of a real-time digitalaudio stream as discussed before. The audio data is held in the payloadsection 211 or portion of the data packages 200 a, 200 b as discussedbefore. The data packages 200 a, 200 b further comprises a headersection in front of the payload section and a package error-detectingcode 213 (e.g. cyclic redundancy check (CRC) code) after the payloadsection. These header and CRC sections of the data packages 200 a, 200 bmay be identical to the header and CRC sections of each of the datapackages 200 c, 200 d which both belong to the second packet categorywithout audio data. The header sections of the data packages 200 a, 200b, 200 c, 200 d may comprise an air interface header 201 in a designatedfield of the data packages. The air interface header may comprise apre-ample and a unique access address of the portable communicationdevice in question. The previously discussed acknowledgement indicator203 of the data packages is held in the “ACK” field and may comprise asingle bit or several bits. A predetermined code 205 is held in an “L”portion of the header section. The predetermined code 205 is indicatingthe category of the data package as discussed below in further detail.The field “G-ch” of the header section holds the previously discussedfavoured or “golden” band identifier 207. The payload section 211 orportion of the data package 200 a holds in addition to the audio data a“Control data” field or section 209. The control data section may holdvarious types of control data associated with the operation or state ofthe hearing aid e.g. a command to turn up the volume of the hearing aid,or a switch of audio input channel from e.g. omnidirectional mode todirectional mode etc.

The data package type 200 c belongs to the previously discussed secondpacket category. The data structure and individual data fields of thedata package 200 c are overall identical to the structure of the datapackage 200 a except for the lack of audio data in the payload portionof the data package 200 c. The payload section of the data package 200 ccomprises control data 209 like the payload section of the data package200 a. The data structure and individual data fields of the third typeof data package 200 d are overall identical to the structure of the datapackages 200 a, 200 b except for the lack of a payload portion. Hence,the size of the third type of data package 200 d is smaller than thesecond type of data package 200 c.

The purpose of the predetermined code 205 held in the “L” portion of theheader section of each of the first, second, third and fourth datapackages 200 a, 200 b, 200 c, 200 d is at least indicating a particularcategory of the data package, e.g. indicating whether the data packagebelongs to one of the previously discussed first and second packetcategories. This feature allows the communication controllers of theleft and right hearing aids rapid and efficient processing of a receiveddata package. If the predetermined code L indicates that a particularreceived data package belongs to the second packet category, thecommunication controller in question may, after evaluating the code L,for example know that it can skip looking for audio data in the payloadsection of the received data package. The predetermined code L mayindicate, or point to, an address or position of the data packageholding a particular type of payload data. Hence, the predetermined codeL may for example point to a start address of the control data section209, or CRC section 213 or a start address of the audio data section 211of the data package 200 a, 200 b, 200 c, 200 d. Three differentpredetermined numerical values may for example be assigned to thepredetermined code L of a particular data package in accordance with itstype, i.e. 200 a, 200 b or 200 c, 200 d. Hence, a first value X (e.g. 4)of L points to the start address of the CRC section 213. A second valueof L such as Y (e.g. 24) points to the start address of the audio datasection 211 if there are no control data in the data package. A thirdvalue of L (e.g. 26) points to the start address of the control datasection 209 provided the data package contains both audio data and twobytes of control data. A fourth value of L such as X+2 (e.g. 6) pointsto the start address of the control data section 209 provided the datapackage lacks audio data but includes the two bytes of control data.Hence, the latter scheme for assignment of discrete values to thepredetermined code L allows the communication controller to access andidentify the type of data content and its location in a particularreceived data package by reading and evaluating the code L of thereceived data package. The communication controller may initiallydetermine the packet category of the received data package by readingthe L value and notice that L values of Y and X+Y indicates that thedata package contains audio data. Hence, if the L value of the receiveddata package in question equals Y or X+Y, the communication controllercan determine that the received data package belongs to the first packetcategory while the residual two values of L indicates the second packetcategory. The format of the data package where the predetermined code Lto points the start address of the control data, audio data or otherdata content of the data package leads to compact format, i.e. smallsize of the data package. The compact format is achieved because thedata package structure is free from overhead codes or bits in front ofeach of the individual payload data sections to identify a beginning ofeach of these data sections. The presence of the predetermined code L inthe received data packages also reduces the computation load, andtherefore power consumption, of the communication controller at thereceiving hearing aid or device. The code L allows the communicationcontroller to jump directly to the start addresses of the various dataportions of the received data packages and read the data content thereofinstead of parsing or decoding all data bytes of the received datapackage to find the locations of the desired data portions or fields.The skilled person will understand that other embodiments may lack thispredetermined code L and the relevant data content of the data packageidentified by parsing or evaluating the data package content.

FIG. 4 is a schematic time-frequency diagram or plot 400 of a secondexemplary transmission of data packages P1, P2, P3, P4, P5 and P6 ofdifferent categories between the left and right hearing aids 10L, 10R inaccordance with the previously discussed embodiments. Each of the datapackages P1, P2, P4 and P5 belong to the first packet category asdiscussed before. The data packages P3 and P6 may belong to the secondpacket category with the features and benefits discussed before. Theillustrated second exemplary transmission of data packages willtypically correspond to environmental conditions with moderate levels ofinterfering noise in the utilized frequency band or bands. Hence, thefirst attempt to transmit P1 may be unsuccessful and/or the firstattempt to transmit P2 may be unsuccessful. The utilized data packagetransmission methodology provides retransmission of a lost data packageof the first packet category for a certain maximum number of times, N.The value of N may lie between 1 and 4 as discussed before, but may belarger in alternative embodiments of the data package transmissionmethodology such as 6, 8 or 10. The illustrated second exemplarytransmission of data packages also utilizes the previously discussedfavoured frequency band embodiment such that the first attempt totransmit P1 and P2 in the first connection event Ci1 is made on thefavoured frequency band No. 5. Likewise, the first attempt to transmitP4 and P5 in the second connection event Ci2 is made on the favouredfrequency band and so forth for the first attempt to transmit aparticular data package in the following successive connection eventsCi3, Ci4 etc.

The transmission of data packages illustrated on the schematictime-frequency diagram 400 begins once the left (M) and right (S)hearing aids 10L, 10R have been connected following the previouslydiscussed methodology. The communication controller 26L generates thefirst data package P1 with an unset acknowledgement indicator 403 forthe reasons discussed above. P1 is then transmitted to the right hearingaid as outlined before. In the right or slave hearing aid 10R, thecommunication controller 26R is configured to monitoring the wirelesscommunication channel 12 (refer to FIG. 1) for receipt of the first datapackage P1 at a particular time window as discussed above. If and onceP1 is received at the right hearing aid 10R, the communicationcontroller 26R checks whether the data content of P1 is corrupted or notbased on the error-detecting code held in the CRC section of P1. Incontrast to the previous first transmission example, the communicationcontroller 26R now finds a failed CRC check or that P1 is absent at theexpected time window. Hence, the communication controller 26R concludesthat the first attempt to transmit P1 from the right hearing aid wasunsuccessful or a failure because P1 was either not received at the lefthearing aid 10L or P1 had corrupted data. The communication controller26R responds to this finding by generating the data content of the newP2 data package in accordance with the data package layout 200 a (referto FIG. 2) for a data package of the first category. The communicationcontroller 26R leaves the acknowledgement indicator 403 of P2 unset andtransmits P2 to the left hearing aid through the bi-directional wirelesscommunication channel on the favoured frequency band No. 5 since it isthe first attempt to transmit P2. In left hearing aid, the communicationcontroller 26L monitors the favoured frequency band No. 5 awaitingreceipt of P2. If and once P2 is received at the left hearing aid 10L,the communication controller 26L checks whether the data content of P2is corrupted or not based on the error-detecting code of the CRC sectionof P2. In contrast to the previous first transmission example, thecommunication controller 26L finds this time that the CRC check of P2 isvalid but the acknowledgement indicator of P2 is unset. Consequently,the communication controller 26L concludes that the transmission of theprevious data package P1 failed. Since, P1 belongs to the first packetcategory, and only a single transmission attempt has so far been made,the communication controller 26L responds by retransmitting P1 a firsttime, i.e. performing a second transmission of P1.

In connection with making the decision as to whether or not toretransmit P1, the communication controller 26L may be configured tomake an initial detection of the category of P1 by inspection orevaluation of the value of the previously discussed L code held in thepredetermined header field 205 of P1. This is a very efficient way todetermine the packet category of P1. If P1 belongs to the first packetcategory, the communication controller 26L is configured to retransmitP1 a limited number of times during the current connection event, e.g.Ci1, until either a valid data package with a set acknowledgementindicator is received from the right hearing aid or the previouslydiscussed maximum number N of retransmissions P1 is reached. P1 isskipped or flushed once the maximum number of retransmissions N of P1 isreached by the communication controller 26L. Hence, P1 is flushed afterN failed retransmissions of P1 or in other words a total of N+1unsuccessful attempts to transmit P1. If P1 on the other hands belongsto the second packet category, the communication controller 26L maydiscard or skip any further attempts to retransmit P1 in the currentconnection event immediately after a failed first attempt because thedata content of P1 is can be assumed to lack urgency, i.e. not real-timecritical as the case for category 1 data packages with real-time audiodata. The communication controller 26L may detect the category of P1 byinspection of the predetermined value of the code L as discussed above.To ensure the data content of P1 is not lost if P1 belongs to the secondpacket category P1 is preferably retransmitted in the subsequentconnection event to Ci1, e.g. Ci2, in the present example. This processwill lower the power consumption of the left and right hearing aidsbecause the skipped retransmission of P1 under these circumstancesallows quick powering down of the radio transceiver 34L and the radiotransceiver 34R and entry into the idle time period 420. The non-timecritical data content of P1 may instead be added to the control datasection of the first data packet transmitted in the second connectionevent, i.e. P4 in this transmission example.

Reverting to the situation or example where P1 belongs to the firstpacket category, the communication controller 26L is preferablyconfigured to retransmit P1 a first time on a default frequency bandthat is different from the favoured frequency band (No. 5 in thisexample) since the latter may be corrupted by interfering noise asindicated by the failure to transmit P1 at the first attempt on thefavour frequency band. The communication controller 26L has in thepresent example selected frequency band No. 1 as the new and differentfrequency band e.g. as set by the previously discussed connectionparameters to ensure synchronization between left and right hearingaids. The skilled person will understand that other frequency bands ofthe n spaced apart frequency bands could be selected as the defaultfrequency band for the first retransmission. Data packages transmittedsubsequent to the first retransmission of P1 on the new defaultfrequency band No. 1 may be transmitted on frequency bands selected inaccordance with the previously discussed predetermined frequency hoppingkey or scheme as illustrated by selection of frequency band No. 2 forthe first retransmission of P2 and frequency band No. 3 for the firsttransmission of P3. In other words, if the first transmission attempt ofthe first and/or second data package on the favoured frequency bandfails, the transmission scheme for transmission of any further datapackages during a current connection event may revert to a traditionalfrequency hopping scheme based on the current hopping key, e.g. thescheme discussed above. In the right hearing aid 10R, the communicationcontroller 26R is now configured to monitoring the bi-directionalwireless communication channel for receipt of the retransmitted P1package at a particular time window as discussed above. If and once theretransmitted P1 is received at the right hearing aid 10R, thecommunication controller 26R checks, as outlined above, the data contentof the retransmitted P1 inclusive the setting of the acknowledgementindicator. In this example the retransmission of P1 is successful andthe communication controller 26R detects the unset state of theacknowledgement indicator of P1. The unset state of the acknowledgementindicator of P1 indicates a failure of the first attempt to transmit P2from the right hearing aid to the left hearing aid. Furthermore, P2 mustbe retransmitted because it belongs to the first packet category for thereasons discussed above with respect to P1. Hence, the communicationcontroller 26R retrieves or regenerates P2, sets the acknowledgmentindicator of the header of P2 and retransmits P2 for a first time to theleft hearing aid. The communication controller 26R also selects a newfrequency band, band No. 2, for the retransmission of P2 by applying thecurrent hopping key, one, to the previous frequency band. On other hand,had the first retransmission of P1 been a failure, communicationcontroller 26R of the right hearing aid would had retrieved orregenerated P2 with an unset acknowledgment indicator and thenretransmitted P2 to the left hearing aid.

If and once the first retransmission of P2 is received at the lefthearing aid 10L, the communication controller 26L checks once again thedata content of the received P2 package. In contrast to the firstattempt to transmit P2, the communication controller 26L finds this timethat the CRC of P2 is valid and the acknowledgement indicator of P2 isset. Consequently, the communication controller 26L concludes that thefirst retransmission of P1 was successful. Hence, no furtherretransmissions of P1 are required as the audio data of P1 has now beensafely received at the left hearing aid. Furthermore, since P2 wascorrectly received at the left hearing aid, the communication controller26L of the left hearing aid generates and transmits a new, short, datapackage P3 with a set acknowledgement indicator. P3 belongs to thesecond packet category as discussed before. The communication controller26L may in response switch the radio transceiver 34L into the previouslydiscussed idle mode for the residual duration of Ci1 to lower the powerconsumption of the left hearing aid.

On the other hand, had the CRC check of the retransmitted P2 beeninvalid or had P2 been absent at the expected time, the communicationcontroller 26L had concluded that the first retransmission of P1 was afailure too and carried out the earlier outlined steps to retransmit P1for a second time provided the maximum number of retransmissions, N, hadnot been exceeded. Hence, if the value of N had been set to 1, then thecommunication controller 26L would not attempt to retransmit P1 for thesecond time, but instead flush or abandon P1 for the reasons discussedbefore in view of the potential latency problems involved with too manyretransmission of the same data package with real-time audio data. Inthe latter scenario, the first data package P4 transmitted by the lefthearing aid in the second connection event Ci2 would accordingly holdnew and updated audio data in the payload section relative to theflushed audio data of P1.

The skilled person will appreciate that the data of first data packageP1 in the first transmission attempt and the data of the first datapackage in the one or more possible retransmissions of P1 need not beexactly identical, since the setting of the acknowledgement indicatorand/or CRC value may have changed between the first transmission of P1and a subsequent retransmission of P1. The acknowledgement indicator ofthe retransmitted P1 package may reflect the actual receipt failure orreceipt success of the second data package P2 while the acknowledgementindicator of P1 in the first transmission attempt may have thepreviously discussed default setting or value. However, at least thepayload section of the first data package P1 is preferably identicalbetween the first transmission attempt and the one or moreretransmissions. The same applies for the second and third data packagesP2 and P3 and so on.

Once the communication controller 26R of the right hearing aid receivesthe earlier transmitted package P3 and detects a set acknowledgementindicator therein, the communication controller 26R concludes that thefirst retransmission of P2 was successful. The communication controller26R may in response put the radio transceiver 34R into the previouslydiscussed idle mode to lower the power consumption of the right hearingaid. On the hand, had the CRC check of P3 been invalid, or had P3 beenabsent at the expected time, the communication controller 26R hadconcluded that the first retransmission of P2 was a failure too (i.e.like the first transmission attempt of P2). The communication controller26R would then start to retransmit P2 until a data package withacknowledgement is received or until the maximum number ofretransmissions N had been reached. However, as the radio transceiver34L of the left hearing aid has already entered the idle mode, the lefthearing aid will not transmit any further data packages which inresponse leads the communication controller 26R of the right hearing aidto retransmit P2 until the maximum number of retransmissions N isreached. Hence, the lack of an express acknowledgement of receiptindicator from the left hearing aid in respect of P2 may lead the righthearing aid to believe the transmission of P2 was a failure even thoughP2 was actually correctly received at the left hearing aid at the firstretransmission. However, this situation is unproblematic for theoperation of the present transmission methodology or protocol, becausethe communication controller 26R of the right hearing aid simplyproceeds to flush P2 after the N failed retransmissions of P2. In thenext connection event Ci2, the communication controller 26R generatesnew data package P5 with a payload section that comprises updated audiodata relative to the audio data of P2 for the right hearing aid asdiscussed before.

FIG. 5 is a schematic time-frequency diagram or plot 500 of a thirdexemplary transmission of data packages P1, P2, P3, P4 and P5 ofdifferent categories between the left and right hearing aids 10L, 10R inaccordance with the previously discussed embodiments. Each of the datapackages P1, P2, P3 and P4 belong to the first packet category asdiscussed before. The data package P5 may belong to the second packetcategory with the accompanying features and benefits discussed above.The illustrated third exemplary transmission of data packages willtypically correspond to environmental conditions dominated by highlevels of interfering noise in the utilized frequency band or bandsduring the first connection event Ci1. The environmental conditions mayhave improved during the second connection event Ci2. Hence, the firstattempt to transmit P1 may be unsuccessful and/or the first attempt totransmit P2 may be unsuccessful. The subsequent attempts to retransmitP1 and to retransmit P2 during the first connection event Ci1 may allfail as well. The maximum number of retransmissions N of a lost datapackage of the first packet category, i.e. P1 or P2 in the presentexample, has been set to two, i.e. N=2 for both of the left and righthearing aids 10L, 10R in this example but may differ in otherembodiments. The illustrated third exemplary transmission of datapackages also utilizes the previously discussed favoured frequency bandmethodology for the first attempt to transmit a data package in eachconnection event. The transmission of data packages illustrated on theschematic time-frequency diagram 500 begins once the left (M) and right(S) hearing aids 10L, 10R have been connected following the previouslydiscussed methodology. The communication controller 26L generates thefirst data package P1 with an unset acknowledgement indicator 503 asdiscussed before and transmits P1 to the right hearing aid as outlinedbefore. In the right and left hearing aids, the respective communicationcontrollers 26R, 26L are configured to monitoring the wirelesscommunication channel 12 (refer to FIG. 1) for receipt of the first dataand second packages P1, P2 at particular time windows as discussedabove. In the present example, both the first attempt to transmit P1 onthe favoured frequency band No. 5 fails and the first attempt totransmit P2 on the favoured frequency band No. 5 fails, as indicated bypackage exchange session 505 a, for one of the reasons discussed above.The communication controller 26R of the right hearing aid 10R inresponse retransmits P1, still with the unset acknowledgement indicator503, a first time on the default frequency band No. 1 as discussed inconnection with the second exemplary data package transmission. Thecommunication controller 26L of the left hearing aid retransmits P2,with an unset acknowledgement indicator 503, a first time on thefrequency band No. 1 as indicated by the hopping key as discussed inconnection with the second exemplary data package transmission. However,both the first retransmission of P1 fails and the first retransmissionof P2 fails as indicated inside package exchange session 505 b despitethe switching to new frequency bands compared to the favoured frequencyband. The communication controllers 26L, 26R of the left and righthearing aids therefore proceed to make a second retransmission attemptof their respective data packages, P1 and P2, as indicated insidepackage exchange session 505 c. When the communication controller 26L ofthe left hearing aid detects that the acknowledgement indicator 503 ofP2 in the package exchange session 505 c is (still) unset, or that P2 isabsent, the communication controller 26L compares the current number ofretransmissions of P1 with the maximum number of retransmissions N whichis set to two. The communication controller 26L therefore concludes thatthe maximum number of retransmissions P1 has been reached and proceedsto flush or skip P1 rather than attempting yet another retransmission ofP1 for the reasons discussed before. The communication controller 26Lmay therefore proceed by switching to the previously discussed quickpower-down mode of the radio transceiver 34L in expectation of theupcoming idle time period 520. Hence, the communication controller 26Lmay in this situation interrupt the monitoring of the wirelesscommunication channel for incoming data packages, because P1 should notbe retransmitted regardless of the actual setting of the acknowledgementindicator 503 of P2 in the package exchange session 505 c. Thecommunication controller 26R of the right hearing aid proceeds in acorresponding manner once it detects that the acknowledgement indicatorof P1 in the package exchange session 505 c is unset, or that P2 isabsent, the communication controller 26L.

FIG. 6 is a schematic time-frequency diagram or plot 600 of a fourthexemplary transmission of data packages P1, P2, P3, P4, P5 and P6 ofdifferent categories between the left and right hearing aids 10L, 10R inaccordance another embodiment. In the present embodiment, the secondhearing aid generates and transmits only data packages of the secondpacket category while the first hearing aid generates and transmits atleast some audio data packages of the first packet category. Hence, anaudio stream may be transmitted from first to the second hearing aid butnot vice versa. As illustrated, P1 and P4 belong to the first packetcategory while the data packages P2 and P5 transmitted by the secondhearing aid belong to the second packet category. The illustrated thirdexemplary transmission of data packages will typically correspond toenvironmental conditions with low levels of interfering noise in theutilized frequency band or bands during the first and second connectionevents Ci1 and Ci2. Hence, the first attempt to transmit P1 issuccessful and the first attempt to transmit P2 is likewise successful.Hence, the first hearing aid generates the third data package P3 with aset acknowledgement indicator and transmits P3 to the second hearingaid. The latter receives and checks the content of P3 and finds that theacknowledgement indicator of P3 is set and the data of P3 are valid asfor example indicated by the CRC code of P3. Hence the first connectionevent Ci1 is now terminated by the first and second hearing aids. Sincethe present embodiment utilises the golden frequency band procedure, thefirst attempt to transmit the first data package P4 of the subsequentconnection event Ci2 is carried out on frequency band No. 5 and thesecond hearing aid responds to receipt successful receipt of P4 bygenerating and transmitting P5 which in turn is responded to by thefirst hearing aid by generating and transmitting the data package P6 ofthe second packet category since the P4, with its audio data, has beensuccessfully received at the second hearing aid.

FIG. 7 shows the previously discussed schematic time-frequency diagramor plot 700 of the transmission of data packages P1, P2, P3, P4 and P5where the hopping key is set to 1 and no favoured/golden frequency bandscheme is utilized. The data packages P1 and P2, P3 and P4 all belong tothe first packet category. The maximum number of retransmissions of thefirst and second data packages, N, M, respectively, is both set to 2.The illustrated exemplary transmission of data packages will typicallycorrespond to environmental conditions dominated by high levels ofinterfering noise in the utilized frequency band or bands during thefirst connection event Ci1 and much smaller levels of interfering noisein the utilized frequency band or bands during the second connectionevent Ci2. As indicated by the unset acknowledgement indicators of alltransmitted P2 data packages, both the first transmission attempt andthe two subsequent retransmission attempts of the first data package P1failed. Likewise, both the first transmission attempt and the twosubsequent retransmission attempts of the second data package P2 failed.Consequently, the communication controller 26L of the left hearing aidproceeds to flush P1 and the communication controller 26R of the righthearing aid proceeds to flush P2. Hence, there is not transmitted anythird data package during Ci1. During the second connection event Ci2,the communication controller 26L generates the new data package P3 andadds current audio data such as an audio frame to the payload section ofP3. The communication controller 26L sets the previously discusseddefault value of the acknowledgement indicator 703 of P3 and writesother data package sections with appropriate data and finally transmitsP3 to the right hearing aid. The communication controller 26R of theright hearing aid monitors frequency band No. 7 of the wirelesscommunication channel and awaits arrival of P3. Upon receipt of P3, thecommunication controller 26R proceeds as discussed in detail before withreference to FIG. 4 in case of a successful receipt of a data package ofthe first category. Hence, data packages P3, P4 and P5 can be viewed asa first, second and third data package, respectively, of the secondconnection event Ci2.

Although particular embodiments have been shown and described, it willbe understood that it is not intended to limit the claimed inventions tothe preferred embodiments, and it will be obvious to those skilled inthe art that various changes and modifications may be made withoutdepartment from the spirit and scope of the claimed inventions. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. The claimed inventions areintended to cover alternatives, modifications, and equivalents.

The invention claimed is:
 1. A method of exchanging data packagesbetween a first portable communication device and a second portablecommunication device over a bi-directional wireless communicationchannel, where at least one of the first and second portablecommunication devices comprises a hearing instrument, the methodcomprising: generating, by the first portable communication device, afirst plurality of data packages; transmitting the first plurality ofdata packages from the first portable communication device to the secondportable communication device through a plurality of spaced apartfrequency bands distributed across a radio frequency range of thebi-directional wireless communication channel; computing, at the firstwireless communication device or at the second wireless communicationdevice, transmission quality estimators for the respective spaced apartfrequency bands; determining a favoured frequency band based on thetransmission quality estimators; and transmitting, from the firstportable communication device to the second portable communicationdevice, a second plurality of data packages on the favoured frequencyband, the second plurality of data packages comprising a first datapackage; wherein if the transmission of one of the second plurality ofdata packages fails, the method further comprises: selecting, inaccordance with a frequency hopping key, a frequency band of theplurality of spaced apart frequency bands that is different from thefavoured frequency band; and retransmitting the one of the secondplurality of data packages on the different frequency band.
 2. Themethod of exchanging data packages according to claim 1, furthercomprising receiving a second data package transmitted from the secondportable communication device to the first portable communication deviceon the favoured frequency band.
 3. The method of exchanging datapackages according to claim 1, further comprising establishing aplurality of successive connection events through the bi-directionalwireless communication channel; wherein the second plurality of datapackages is transmitted during at least a subset of the plurality ofsuccessive connection events on the favoured frequency band.
 4. Themethod of exchanging data packages according to claim 1, wherein one ofthe second plurality of data packages comprises a header section, apayload section, and a data check section holding a packageerror-detection code.
 5. The method of exchanging data packagesaccording to claim 4, further comprising adding a band identifierindicating the favoured frequency band to a predetermined header fieldof the header section.
 6. The method of exchanging data packagesaccording claim 1, wherein a first subset of the second plurality ofdata packages transmitted by the first portable communication devicebelongs to a first packet category comprising audio data, and a secondsubset of the second plurality of data packages belongs to a secondpacket category without audio data.
 7. The method of exchanging datapackages according to claim 6, wherein a size of the data packages inthe second subset belonging to the second packet category is smallerthan a size of the data packages in the first subset belonging to thefirst packet category.
 8. The method of exchanging data packagesaccording to claim 1, further comprising adding a first plurality ofacknowledgement indicators, at the first portable communication device,to the first plurality of data packages before they are transmitted bythe first portable communication device, wherein at least a subset ofthe first plurality of acknowledgement indicators indicates whether aprevious data package was successfully received at the first portablecommunication device.
 9. The method of exchanging data packagesaccording to claim 8, further comprising adding a second plurality ofacknowledgement indicators, at the second portable communication device,to a third plurality of data packages before they are transmitted by thesecond portable communication device, wherein at least a subset of thesecond plurality of acknowledgement indicators indicates whether aprevious data package was successfully received at the second portablecommunication device.
 10. The method of exchanging data packagesaccording to claim 1, further comprising receiving a second data packageat the first portable communication device; wherein if anacknowledgement indicator of the second data package is set: the methodfurther comprises generating, at the first portable communicationdevice, a third data package comprising an acknowledgment indicatorsetting reflecting successful or failed receipt of the second datapackage, and transmitting the third data package to the second portablecommunication device.
 11. The method of exchanging data packagesaccording to claim 1, wherein if the first portable communication devicefails to receive a second data package or if an acknowledgementindicator of the second data package is unset: the method furthercomprises setting an acknowledgment indicator of one of the secondplurality of data packages to reflect a failed receipt of the seconddata package, and retransmitting the one of the second plurality of datapackages from the first portable communication device to the secondportable communication device.
 12. The method of exchanging datapackages according to claim 11, wherein act of retransmitting the one ofthe second plurality of data packages is performed if the one of thesecond plurality of data packages belongs to a packet category.
 13. Themethod of exchanging data packages according to claim 1, furthercomprising: generating, by the second portable communication device, asecond data package with an acknowledgment indicator setting reflectingsuccessful or failed receipt of one of the first or second plurality ofdata packages; and transmitting the second data package from the secondportable communication device to the first portable communication devicethrough the bi-directional wireless communication channel.
 14. A methodof exchanging data packages between a first portable communicationdevice and a second portable communication device over a bi-directionalwireless communication channel, where at least one of the first andsecond portable communication devices comprises a hearing instrument,the method comprising: generating, by the first portable communicationdevice, a first plurality of data packages; transmitting the firstplurality of data packages from the first portable communication deviceto the second portable communication device through a plurality ofspaced apart frequency bands distributed across a radio frequency rangeof the bi-directional wireless communication channel; computing, at thefirst wireless communication device or at the second wirelesscommunication device, transmission quality estimators for the respectivespaced apart frequency bands; determining a favoured frequency bandbased on the transmission quality estimators; and transmitting, from thefirst portable communication device to the second portable communicationdevice, a second plurality of data packages on the favoured frequencyband, the second plurality of data packages comprising a first datapackage; wherein a first subset of the second plurality of data packagestransmitted by the first portable communication device belongs to afirst packet category comprising audio data, and a second subset of thesecond plurality of data packages belongs to a second packet categorywithout audio data; wherein if the transmission of one of the secondplurality of data packages fails, the method further comprisesretransmitting the one of the second plurality of data packages for atmost N times if the one of the second plurality of data packages belongsto the first packet category; and wherein N is a positive integerbetween 1 and
 4. 15. A method of exchanging data packages between afirst portable communication device and a second portable communicationdevice over a bi-directional wireless communication channel, where atleast one of the first and second portable communication devicescomprises a hearing instrument, the method comprising: generating, bythe first portable communication device, a first plurality of datapackages; transmitting the first plurality of data packages from thefirst portable communication device to the second portable communicationdevice through a plurality of spaced apart frequency bands distributedacross a radio frequency range of the bi-directional wirelesscommunication channel; computing, at the first wireless communicationdevice or at the second wireless communication device, transmissionquality estimators for the respective spaced apart frequency bands;determining a favoured frequency band based on the transmission qualityestimators; transmitting, from the first portable communication deviceto the second portable communication device, a second plurality of datapackages on the favoured frequency band, the second plurality of datapackages comprising a first data package; receiving a second datapackage at the first portable communication device; and checking anerror-detection code of the second data package subsequent to receipt ofthe second data package at the first portable communication device;wherein if the error-detection code indicates invalid data of the seconddata package, the method further comprises ignoring a setting of anacknowledgment indicator of the second data package, and unsetting anacknowledgment indicator of a third data package to reflect a failedreceipt of the second data package.